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c#.netarrays
GaGar1n
GaGar1n

Reputation: 1040

Dynamically created jagged rectangular array

In my project I have a lot of code like this:

int[][] a = new int[firstDimension][];
for (int i=0; i<firstDimension; i++)
{
  a[i] = new int[secondDimension];
}

Types of elements are different.

Is there any way of writing a method like

createArray(typeof(int), firstDimension, secondDimension);

and getting new int[firstDimension][secondDimension]?

Once again, type of elements is known only at runtime.

Upvotes: 9

Views: 6961

Answers (4)

Henk Holterman
Henk Holterman

Reputation: 273494

Generics should do the trick:

static T[][] CreateArray<T>(int rows, int cols)
{
    T[][] array = new T[rows][];
    for (int i = 0; i < array.GetLength(0); i++)
        array[i] = new T[cols];

    return array;
}

You do have to specify the type when calling this:

char[][] data = CreateArray<char>(10, 20);

Upvotes: 11

Pete
Pete

Reputation: 11495

If:

  • You definitely want a jagged array, and not a multi-dimensional one as mOsa mentions.
  • You definitely need it to be of dynamic type at runtime, and not at compile time using generics as Henk mentions.

You can use Array.CreateInstance something like:

static Array CreateArray (Type t, int rows, int cols)
{

    Array arr = Array.CreateInstance (typeof(Array), rows);
    for (int i = 0; i < rows; rows++) {
        arr.SetValue (Array.CreateInstance(t, cols), i);
    }

    return arr;
}

But are you sure you need this to by dynamic type at runtime?

Upvotes: 1

Alastair Pitts
Alastair Pitts

Reputation: 19601

As mOsa mentioned, if you want rectangular jagged array, then you are better off using a multi-dimensional array.

int[,] array = new int[dimension, dimension2];

will generate a rectangular array.

The reason to use a jagged array, is if you want to create an array with different secondary dimensions. A jagged array is really an array of arrays, where as a multi-dimensional array is a slightly different beast.

Upvotes: -1

m0sa
m0sa

Reputation: 10940

Well you can do this:

int[,] array = new int[4,2];

What you get is called a multidimensional array (4x2). Here is a nice article about multidimensional arrays.

The term jagged array usually refers to arrays, that have different second dimensions. For example take:

int[][] jagged = new int[2][];
jagged[0] = new int[5]; // 5 elements
jagged[1] = new int[1]; // 1 element

so this is not a 2x5 array, but a jagged array..

Upvotes: 1

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